Don't copy attributes that don't exist to partial instances

Classes don't have an `__name__` attribute, so when wrapping them in a `functools.partial` instance, don't try to copy it. Same goes for `__doc__`, but most objects should have that.

src/milla/dispatch/routing.py

@@ -50,8 +50,10 @@ class Router(object):
                     urlvars = match.groupdict()
                     urlvars.update(vars)
                     func = functools.partial(controller, **urlvars)
-                    func.__name__ = controller.__name__
-                    func.__doc__ = controller.__doc__
+                    if hasattr(func, '__name__'):
+                        func.__name__ = controller.__name__
+                    if hasattr(func, '__doc__'):
+                        func.__doc__ = controller.__doc__
                     self._cache[path_info] = func
                     return func
         raise UnresolvedPath